Hoses are useful for transporting fluid, conveying power or transmitting pressure in all kinds of applications. A hose comprises an internal polymer lining or tube to keep the fluid inside and a reinforced wall to withstand the pressure of the fluid. The product of pressure in a hose and its diameter must not exceed twice the strength of the wall reinforcement per unit length as otherwise the hose will burst. Adequate safety factors have to be taken into account for all kinds of losses emanating from the build of the hose and the intended use of the hose.
The reinforcement in the wall is therefore chosen as a function of the pressure that has to be held by the hose. For high pressure hoses (operating above 7 MPa) generally steel wire is chosen as reinforcement as it combines the required strength with flexibility, adhesion, and a predictable lifetime. In order to protect the steel wire from outside influences it may be covered with a polymer mantle such as an extruded rubber cover although the reinforcement may also remain visible when for example stainless steel types of wires are used.
The reinforcing wires are applied around the inner tube through braiding or spiralling or even sometimes a combination of both. In a spiralled hose consecutive layers of parallel steel wires are wound around the inner polymer tube in alternating directions with different lay lengths. In braiding, ribbons of parallel steel wires are maypole braided around the inner tube. A circular weaving pattern emerges that can have many arrangements such as plain, twill or satin weave. In a braided reinforcement the number of crossovers per unit length i.e. places where a ribbon in one direction crosses a ribbon in the other direction is reduced to a minimum. This can be done by broadening the ribbon i.e. by taking more filaments into the ribbon or by using a 2×2 twill (2 over, 2 under), 3×3 twill (3 over, three under) or even satin weave.
In both braiding and spiralling steel wire ribbons are given a certain degree of preforming by guiding them over a performer pin prior to embedding them into the layer of a hose. By this preforming the wires obtain a helicoidal shape that fits the winding of the wires in the reinforcement layer.
The lay lengths are chosen in order to have as little as possible contraction or elongation of the hose in axial length when pressure is applied to the hose. Therefore lay angles—the angle between the axis of the hose and the reinforcement—are kept close to the ‘neutral angle’ that is A tan(√{square root over (2)}) or about 54°44′.
Recent attempts have been made to further improve the performance of hoses by:                Using crimped or bent wires in order to tune the mechanical properties of subsequent layers better to one another (WO 2015/000773 A1);        Using flattened high-tensile wires (WO 2005/108846 A1). Flattened high-tensile wires have a higher ductility than the round wires they originate from. This makes the wire better suited for incorporation into a hose. Also flattened wires result in an overall lower thickness of the hose. Further, at the cross-overs, flat wire surfaces are in contact with one another, thereby reducing the transversal contact stresses. Round wires—in particular high and ultra-high tensile strength wires—are prone to loss in breaking load when subject to transversal stresses. Moreover the round-on-round contacts at the crossovers result in increased erosion fatigue when the hose is dynamically loaded resulting in an early failure of the hose. Although the use of flattened steel reinforcement wires results in improved hoses, the processing of the flattened wires into a ribbon is not easy as sometimes a single flattened wire tends to twist, thereby creating a spot in the hose that can succumb when the hose is pressurised.        Using strips of steel wires or steel cords embedded in a polymer (WO 2001/092771 A1). However, with this kind of arrangement not enough ‘transversal strength’ can be obtained. With ‘transversal strength’ is meant the breaking force of the strip divided by the width of the strip. There must remain a substantial amount of polymer in between the steel wires or steel cords to keep them together in a strip. Moreover, the polymer encapsulation inhibits the use of the strip in a machine with preformers.        In this respect it has been suggested to preform the polymer strips with steel cords embedded during manufacturing (WO 2007/009873 A2). But also there the problem remains that the ‘transversal strength’ is inferior to what can be achieved with the prior art ribbons.        
Generally, hose reinforcement wire is covered with a brass coating to enable adhesion to rubber. However, there are a lot of alternative organic coatings that have been suggested in order to have a steel surface adhere to a rubber or polymer. The most notable are those compounds having two functional groups: one directed for adhesion to the polymer, one directed for co-valent bonding to steel. See e.g. US2002/0061409, U.S. Pat. No. 3,857,726 and references therein. These systems focus on having a good bond transition between the steel wire with a high modulus and the low modulus of the rubber or polymer in which the steel wire is intended to be used. It is not an object of these disclosures to bond steel wires to one another with sufficient mechanical strength.
The inventors have therefore sought other ways to solve the problems mentioned.